This invention relates generally to intraocular lenses designed for implantation into the eye as a replacement for a surgically removed natural lens. More specifically, this invention relates to an improved intraocular lens designed for posterior chamber implantation and including means for positive seating of resilient centering and fixation loops for the lens within the capsular bag in the posterior chamber of the eye.
Intraocular lenses in general are well known for implantation into the eye as a replacement for a natural crystalline lens which has been removed surgically due to a cataract condition, injury, or the like. Such intraocular lenses typically are constructed from a transparent lens body of a selected, relatively inert plastic material, such as polymethylmethacrylate, having a generally disk-shaped configuration providing optical characteristics approximating a natural lens. Resilient support loops are normally provided to project outwardly from the periphery of the lens body with a smooth, outwardly convex curvature for supporting and centering the lens body with respect to adjacent delicate eye tissue. In accordance with some intraocular lens configurations, the lens body and support loops are designed for seating in the so-called anterior chamber of the eye in front of the iris and pupil, whereas other lens designs are intended for implantation within the so-called posterior chamber behind the iris and pupil.
In accordance with recent trends in ophthalmic surgery, posterior chamber lens implantation is preferred by many surgeons largely because the lens prosthesis is positioned within the eye at or near the original position of the natural lens. More particularly, posterior chamber implantation of an intraocular lens commonly follows so-called extracapsular extraction wherein a central anterior wall region of a transparent capsular bag or membrane containing the natural lens is surgically removed to accomodate natural lens removal while leaving the remainder of the capsular bag intact. The intraocular lens implant is then inserted through the pupil margin into the posterior chamber desirably with the resilient support loops seated within the periphery of the capsular bag.
Implantation of an intraocular lens including the resilient support loops fully into the capsular bag, however, constitutes a relatively difficult surgical procedure. In particular, the lens implant is normally held in an angular orientation during insertion through a corneal incision and further through the pupil into the posterior chamber with one of the loops leading lens insertion and thus angled downwardly for relatively easy seating into the capsular bag, typically within the inferior margin thereof. However, significant lens manipulation is normally required to fit the trailing support loop through the pupilary margin and further to manipulate the trailing loop for seating within the capsular bag, as opposed to seating against the more sensitive ciliary sulcus region within the posterior chamber forwardly of the ciliary muscle and the capsular bag. Such manipulation normally requires sequential insertion into the eye of different surgical instruments thereby prolonging the surgical procedure and increasing risk of eye trauma, particularly to endothelial cells on the interior of the cornea. More- over, the superior margin of the capsular bag into which the trailing loop desirably fits is extremely difficult or impossible for the surgeon to see, whereby positive seating of the trailing loop into the capsular bag frequently cannot be assured.
There exists, therefore, a significant need for an improved intraocular lens designed for positive implantation into the capsular bag within the posterior chamber of the eye following extracapsular extraction, wherein the improved lens is implanted by use of a single surgical instrument inserted into the eye a single time. The present invention fulfills these need and provides further related advantages.